The use of fluidized bed reactors for the incineration of waste fuels, such as municipal refuse containing tramp material, is generally known and involves the burning of the waste fuels with air while fluidizing it in a fluidized bed. In order to improve the combustion along with the fluidizing of the waste fuels, a bed make-up material, such as crushed limestone, sand, and/or clay are fed together with the waste fuels to the fluidized bed.
A typical fluidized bed reactor for the incineration of the waste fuels is equipped with a bar grate in the lower section of the reactor body which is designed to provide fluidizing air to the fluidized bed while allowing ash, spent bed make-up material and tramp material to pass through the spaces between a plurality of bars disposed in the bar grate. The upper section of the reactor body is equipped with a waste fuel feeding unit and a bed make-up material feeding unit. The waste fuel is burned while the waste fuel and the bed make-up material are fluidized by primary air which is blown out through air nozzles connected to the bars. The bars are typically lined with a suitable insulating material, such as a furnace refractory.
The waste fuels are generally of low calorie content and contain a high percentage of tramp material that does not burn. As the waste fuels are fed to the fluidized bed, the volatile organic compounds are burned and the tramp material, such as bottles and cans, as well as ash and spent bed make-up material, are left in the fluidized bed.
As the organic compounds are decomposed and burned within the fluidizing bed, the tramp material, along with the spent bed make-up material and ash, descends downwardly through the reactor and passes through the spaces between the bars disposed in the bar grate. The bed material is thus discharged to external equipment and a portion of the bed make-up material is separated from the tramp material and returned to the fluidized bed.
Conventionally, such reactors use refractory materials to line the surfaces of the bars disposed in the bar grate to insulate the bars from the elevated temperatures in the lower section of the reactor. The elevated temperatures result in the adhesion of slag particles to the refractory lining in the reactor resulting in the slow erosion and subsequent maintenance of the refractory materials. Consequently, such reactors use excessive amounts of fluidizing gases in order to lower the temperature within the reactor and thereby reduce the maintenance costs associated with the repair and replacement of the refractory materials within the reactor. In spite of this precaution, refractories within such reactors must undergo frequent routine maintenance and must be completely replaced approximately every other year.